Tempering furnace



Oct. 13, 1931. w. GROTHE 1,827,194

TEMPERING FURNACE Filed Aug. 27, 1928 3 Sheebs-Sheerl l /r j@ 4/ v\ ATTO w. GROTHE TEMPERING FURNACE Filed Aug. 27, '192s Oct. 13, 1931. 1,827,194

5 Sheets-Sheet 2 FlEL- FQIELB- Oct. 13, 1931. w. GROTHE 1,827,194

TEMPERING FURNACE Filed Aug. 27. 1928 3 Sheets-Sheet l5 IAVENTOR Waker /olhz ATTORNEYS' :Patented Oct. 13, 1931 'y UNITED STATES PATENror-'Flcu WALTER GROTEE, OF SAN LEANDRO, CALIFORNIA, ASSIGNOR T CATERPILLAR TRACTOR C0., OF SAN LEANDRO, CALIFORNIA, A CORPORATION OF CALIFORNIA TEMPERING FURNACE Application led .August 27, 1928. Serial lo. 302,803.

My invention relates to tempering furnaces usually referred to as of the pit type and preferably employing electric heating and forced air circulation.` In furnaces ofy 'gj this kind which heretofore have been used,

there has been difficulty in providing a suitable drive for the air circulating means. The heat radiated by the furnace has practically enforced a remote location of the driving means and has fostered constructions in which the blower fan is driven thru the intermediary of involved shafting and other transmission mechanism which not only complicates the drive considerably, but also is inconvenient and is a source of trouble, particularly in large installations. These considerations become pronounced when the power is furnished by an electric motor, as the consequences ofvan overheated electric motor are apt to be serious.

Itis therefore an object of my invention to provide means for .positively maintaining the drive motor at the proper temperature.

Another object of my lnvention is to do away with cumbersome and involved' power transmission mechanisms.

An additional object of my invention is to provide a novel mounting for the electric heating element.

improve in general furnaces of thisr type in order to provide better operation and increased economy. f

The foregoing and other objects are at tained in the embodiment of the invention shown'in the drawings, in which Fig. 1 is a. transverse section on a vertical plane thru a furnace builtin accordance wlth my invention.

Fig. 2 isa fragmentary view showing 1n cross section a modified arrangement of the air distributing vanes.

Fig. 3 is a plan of the furnacevshown 1n Fig. 1, a portion, however, being disclosed in cross section, the plane of section being indicated byline 3-3 of Fig. 1.

Fig. 4 shows in cross section a detail of the locating pin.

Fig. 5 shows a preferred vform of cover with the motor shaft extending entirely An additional object of my invention is to4 vshell of insulating material within which is situated a removable inner shell carrying electric heating elements, the whole being closed lg' a displaceable cover carrying an electric riving motor with a connection to an air circulating fan mounted on the cover and provided with means to prevent the motor from overheating.

In the modification disclosed particularly in Fig. 1, the furnace comprises an outer, cuplike shell 6 made lp of insulating refractory material 7, enclosed in a metallic sheet 8 which is preferably located with a considerable portion below the floor 9 to increase the accessibility of the assembly. The outer shell 6 encompasses a central cylindrical chamber within which is located an inner metallic shell 11 of such diameter that a surrounding annular space remains. This yprovides room for electric heating elements 12 which are sustamed by supports 13 fastened to a sub-frame 15 mounted on the irmer shell 11. The elements 12 are connected to a suitable source of current, not shown, by 'leads 14 passing thru a bushing 16.

Not only is the inner shell 11 annularly spaced from the outer shell 6, but it also is supported a predetermined distance above the bottom of the outer shell. 4This is accomplished by resting the shell 11 on supports 17 which preferably pass thru the insulating material 7 of the outer shell and rest on the foundation 18 of the furnace. The supports 17 usually are hollow to receivey downwardly extending lugs 19 secured to the bottom of the r tinuous, the bottom wall is customarily perforated to permit the ready circulation of air. To this end the bottom is conveniently formed of a number of parallel slats 23 of ample strength to support directly work being treated or to support a basket or other container for the work.

The upper side of the cup-like outer shell 6 is preferably closed by a displaceable cover 24 suitably fabricated of an exterior metallic covering 26 filled with refractory insulating material 27 of a proper kind and is braced to withstand the strain imposed upon it. The cover 24 can, as shown in Fig. 1. rest on the refractory material 7 nia-king up the outer shell or can be of sufficient diameter, as shown in Fig. .5, to rest directly on the outer sheet 8 thereby removing most of the supporting strain from the insulating material.

To render the cover 24 easily removable and displaceable, it is preferably suspended by a flanged collar 28 from an overhanging arm 29 with rather a loose junction to permit some independent movement of the cover in seating on the outer shell. The arm 29 is joined to a piston 31 operating in a cylinder 32 located on the foundation 18. Suitable pressure fluid, either pneumatic or hydraulic, is ad# mitted to the cylinder 32 thru a passage 33 at the will of the operator. The position of the piston 31 vertically is thus readily adjusted. In any vertical position of the cover affording sufficient clearance, the piston 31 and the cover 24 carried thereby can readily be rotated manually by -the aid of a projecting handle 34 fastened to the arm 29.

In order to maintain an even temperat-ure thruout my furnace,`I have preferablyprovided means for circulating currents of air -thruout the interior thereof in predetermined paths and in predetermined directions. To this end I provide a depending portion 36 on the cover 24 andv journal in this portion an air circulating fan 37. Surrounding the fan' is a shroud 38 and suitable baffles 39 and 41 which control .theinflux and efflux of air to and from the fan. The shroud and baffles are suitably supported by rods 42 secured to the sheath 26 of the cover. As disclosed in Fig. 1, one direction of rotation of the fan causes the air current to progress upwardly thru the annular space between the outer shell 6 and the inner shell 11 and then flow downwardly thru the central compartment and thru the slats 23. A metallic cone 43 located on the bottom of the outer shell 6 not only serves t0 distribute the air at that end of the furnace, but also, due to its shape, is unlikely to buckle or warp under the influence of the heat within the furnace. If the direction of rotation of the fan 37 is reversed, the current of air is also reversed in direction, passing from the interior of inner shell 11 upwardly and thence downwardly on the outside of the shell and over the electric heating elements 12. In Fig.

2 is disclosed a modified arrangement of the baiiies which is designed for operation with either direction of air flow, but is particularly adapted to cause a circulation over the central part of the charge within the inner shell 11 rather than around the edges thereof.

In order to rotate the fan 37 I have provided an electric motor 44. This is preferably mounted on the cover 24, in accordance with my invention, thereby obviating cumbersome drive mechanism. As shown in Fig. 5, one way of connecting the 'fan 37 to the motor 44 is by means of a continuous drive shaft 46 which passes thru the relatively thick insulating material 27 of the cover. The shaft is enclosed in a tubular casing 47 and is provided with no special bearings of its own. The motor is suitably mounted in the collar 28, which is attached to the cover 24, so that the motor bearings carry the drive shaft and the fan. Vent holes 48 pierce the collar. For ordinary temperatures the radiation of heat from this structure is ample to prevent overheating of the motor 44,

For some installations Where a great amount of heat must be radiated to prevent the motor from overheating, I provide the motor driving connection disclosed in Fig. 6. In this case the fan 37 is mounted at the lower end of a hollow drive shaft 49 which is provided with air circulation apertures 50 so that a current of air can pass freely thru the shaft. Bearings 51 and 52 suit-ably mounted in a sleeve 53 support the drive shaft. The sleeve 53 provides a cylindrical depression in the wall of the furnace cover thru which air can freely circulate. Access to the sleeve is attained thru the 'apertured collar 28. Suitable lubricating means 54 are provided for the bearings which. with the shaft 49, are cooled under forced draft from a fan 56 secured to and rotatable with the drive shaft 49. At its upper end, the shaft 49 is joined by a coupling 57 to the drive lmotor 44. It will be noted that air has free access to the drive shaft both interiorly and exteriorly thruout the major portion of the length of the shaft. while a forced draft thru the sleeve 53 and thru the shaft is provided by the auxiliary fan 56.

In the operation of my furnace, the interior shell is put in position after 'the cover has been displaced to one side thru operation of the lift 31. After the inner shell is pinned in place, as at 21, and the heating elements are connected to a source of elec'- tro-motive force. the furnace is charged with material to be treated. Suitable operation of the lift and of the manually controlled lever 34 replaces the cover on the furnace and the treating operation is then begun by energizing the electric heating elements. During the treatment, the motor is operated to rotate the fan 37 thereby inducing a flow of air thruout the interior of the furnace so that a uniform temperature is maintained at all parts thereof. During this operation the heat is removed from the drive shaft before it has a chance to reach the motor so that the motor cannot become overheated. At the conclusion of the treatment, the cover is displaced andthe contents of the inner chamber. Furthermore, the drive for the fan is extremely simple and accessible so that the entire operation of the furnacey is markedly superior to the operation of those heretofore available. f

1. A furnace comprising a substantially imperforate, cup-shaped outer shell, a reu movable cover for closing said shel1,-rotating `mechanism adapted to operate Within. said shell, driving means for said mechanism,

mountings for said rotating mechanism and said drivingmeans adapted to be removed in unison with said cover and support means engaging said mountings for carrying substantially the weight of said rotating mechanism vand said driving means. l

2.- A furnace comprising a heat insulating wall, a fan on one side of said wall, a motor on the other side of said wall, a hollow driving shaft connecting said fan and said motor, and means for forcing cooling air to circulate through said shaft, said wall having a passage therethrough whereby said circulated air escapes directly to the atmosphere.

3. A furnace comprising a heat insulating wall having a` cylindrical depression therein, a hollow driving shaft passing through said wall and being annularly spaced from the ysides of said depression, and a` fan mounted on said shaft for forcing cooling air through said depression and through said shaft.

4. A furnace comprising a shell, a displaceable cover formed of substantially only heat insulating material on said shell, means for circulating air within said shell, means mounted upon said cover for driving. directly said circulating means, and means ad'acent to said shell for supporting saidr circu ating and said driving means so that said cover does not support said means.

5. A-furnace comprising a shell, a displaceable cover formed of heatinsulating material and incapable of supporting a relativel hea load, means for circulating air within sai shell positioned on said cover,

cover, and means independent o supporting said circulating means and carrying the weight thereof. v i

6. A furnace comprising an outer shell enclosing a space to be heated, a fan positioned in saidspace, a shaft for supporting the fan,

-said shaft being hollow for a portion of its length and being supported over a portion of its length in spaced relationship to the shell, and means for forcing air through the hollow shaft and about the portion of the shaft in spaced relationship to the shell.

` 7. A furnace comprising a lshell enclosing a space to be heated, a displaceable cover for positioning on the shell, means for circulating a fluid to heat said space, means for driving said circulating means, both of said means being disposed substantiallfy upon the the cover for carrying the weight of both of said means.

8. A furnace comprising a shell, a cover for said shell, a fan positioned on said cover, a motor having a shaft for driving connection to said fan, and means independent of the cover for supporting the motor so that the weight .of the motor is not normally carried onthe cover. l l

Y9. In a furnace, a fluid circulating unit comprising, a fan, a support independent of the furnace for the fan, a motor carried by the support for driving the fan, and a cover upon which the fan is mounted, the cover being carried yby the sup ort.

10. In a furnace, an outer s ell of refractory material, top and bottom closures therefor of refractory material, an inner metallic shell spaced from said outer shell and said closures and provided with a floor having apertures, a support for said inner shell, removable means to attach said inner shell to 'said support, and heating elementssupported entirely on said inner shell.

11. In a furnace, an insulated chamber, la metal work receptacle ada ted to be placed in said chamber, a support or said receptacle to maintain space between said receptacle and said chamber for air circulation, and

heating elements supported entirely on said receptacle and adapted to be disposed in sald space upon placement of said' receptacle in said chamber on said su port.

In testimony whereo I have hereunto set i and means `independent of said cover for 

